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Title: Phylogenetic analysis of seven WRKY genes across the palm subtribe Attaleinae (Areceaceae) identifies Syagrus as sister to the coconut

Author
item Meerow, Alan
item BORRONE, JAMES - Oklahoma State University
item COUVREUR, THOMAS - New York Botanical Garden
item MAURO-HERRERA, MARGARITA - Oklahoma State University
item HAHN, WILLIAM - Georgetown University
item Kuhn, David
item Nakamura, Kyoko
item Schnell Ii, Raymond

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2009
Publication Date: 10/6/2009
Citation: Meerow, A.W., Borrone, J.W., Couvreur, T.L., Mauro-Herrera, M., Hahn, W.J., Kuhn, D.N., Nakamura, K., Schnell Ii, R.J. 2009. Phylogenetic analysis of seven WRKY genes across the palm subtribe Attaleinae (Areceaceae) identifies Syagrus as sister to the coconut. PLoS One. DOI http://dx.plos.org/10.1371/journal.pone.0007353

Interpretive Summary: Cocos nucifera L., the coconut, is a charismatic monotypic genus forming a dominant part of coastal vegetation across the tropics, and a universal symbol of the tropics in the popular imagination. It is also one of the most economically important palms in the world, and a beloved ornamental tree in tropical regions. The origins of the coconut (Cocos nucifera) have been one of the "abominable mysteries" of palm evolution for decades. Using DNA sequences of seven single copy nuclear genes, we show that the ancestry of the coconut is in South America, and identify the genus Syagrus as the most closely related genus to coconut. We present the most fully resolved family tree of the group of palms to which coconut belongs. Moreover, we introduce seven DNA markers that will have broad use for understanding both populations genetics and species relationships in a large group of palms.

Technical Abstract: The origins of the coconut (Cocos nucifera) have been one of the "abominable mysteries" of palm systematics for decades. Previous studies with predominantly plastid genes have indicated an American ancestry for the coconut but with weak support and ambiguous sister relationships. We used primers designed from seven putatively single copy WRKY transcription factor loci isolated from Cocos nucifera across all genera of the palm tribe Cocoseae subtribe Attaleinae and three outgroup taxa representing subtribes Bactridinae and Elaeidinae. Maximum parsimony, maximum likelihood, and Bayesian analysis of the combined data matrix all produce congruent and well-resolved topologies. Syagrus (inclusive of Lytocaryum) is resolved as monophyletic, and is the sister genus to Cocos nucifera with strong bootstrap support (BP), confirming American ancestry for the genus Cocos. The divergence of Cocos from Syagrus is estimated as 27 MYBP. Attalea and Butia are also consistently resolved as monophyletic, and Jubaea is robustly sister to Butia. Allagoptera, Parajubaea and Polyandrococos form a clade with 95% BP that is supported by leaf anatomical evidence. Subclades within Syagrus and Attalea are often congruent with morphological and/or biogeographic data. Establishment of the two major clades of American Attaleinae appears to have occurred in the Oligocene (ca. 30 MYBP), with subsequent cladogenesis at the Oligocene-Miocene boundary. Much of the subsequent diversification in the Attaleinae can be attributed to the Andean uplift from the late Miocene through the Pliocene-Pleistocene. WRKY loci show promise for investigating phylogenetic relationships within Arecaceae, especially in other tribes of the subfamily Arecoideae.